Sliding piston pressure indicator

ABSTRACT

A fluid pressure indicating device is disclosed. The pressure indicating device includes a housing defining a cylindrical bore therein, and a piston movably disposed within the cylindrical bore. The housing includes a first portion that is permeable to visible light, a first end member, and a second end member opposite the first end member. A first variable volume is defined by the cylindrical bore, the piston, and the first end member of the housing. An inlet port is defined by the first end member of the housing and is in fluid communication with the first variable volume. A piston bypass channel is disposed outside the cylindrical bore and is in fluid communication with the inlet port. An outlet port is defined by the second end member, such that the outlet port is in fluid communication with the piston bypass channel.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/784,772, filed on Mar. 14, 2013, and of U.S. Provisional ApplicationNo. 61/813,072, filed on Apr. 17, 2013, the disclosures of which arehereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to pressure indicators. Moreparticularly, the present invention relates to a pressure indicatorsuitable for an inflatable cuff of an endotracheal tube.

BACKGROUND OF THE INVENTION

Inflatable cuffs have been proposed for applying occlusive pressure to aflow lumen of a patient's body, or for sealing between a medicalinstrument and a flow lumen of a patient's body. For example, anendotracheal tube may include an inflatable cuff that conforms to thecontours of a patient's trachea when inserted into the trachea andinflated to seal a gap between the endotracheal tube and the trachea.Further, pressure indicators have been proposed for monitoring a fluidpressure within an inflatable cuff

U.S. Pat. No. 4,727,887 (hereinafter “the '887 patent”) describes anartificial sphincter with an occlusion cuff for applying occlusivepressure to a flow lumen of a patient's body (e.g., a urethra). The '887patent further proposes a combination hypodermic manometer including apiston assembly which is adapted for reciprocal movement through afluid-filled sleeve. As the piston assembly of the '887 patent is movedthrough the sleeve, a bellows is compressed, thereby changing a heightof fluid within a manometer fluidly coupled to the bellows. However,accuracy of the hypodermic manometer of the '887 patent may depend uponorientation of the manometer with respect to gravity, making itdifficult to use with accuracy in practice. Moreover, a rupture or leakof the bellows poses the risk of mixing the manometer fluid with thefluid in contact with the occlusive cuff.

Pressure indicators including a bellows within a hollow housing made ofa transparent material, such that an indicator mark on the bellows isvisible through the housing, are known for use with pressure cuffdevices. However, accuracy of such indicators may be sensitive tovariations in the resilience of the bellows, which in turn is sensitiveto variations in bellows geometric and material properties.

Accordingly, methods and apparatus are desired for indicating pressurein an inflatable cuff that are insensitive to geometric and materialvariations, and that are insensitive to the spatial orientation of theapparatus.

SUMMARY OF THE INVENTION

One aspect of the present invention advantageously provides a pressureindicating device including a housing defining a cylindrical boretherein, and a piston movably disposed within the cylindrical bore. Thehousing includes a first portion that is permeable to visible light, afirst end member, and a second end member opposite the first end member.A first variable volume is defined by the cylindrical bore, the piston,and the first end member of the housing. A second variable volume isdefined by the cylindrical bore, the piston, and the second end memberof the housing, such that the second variable volume is sealed betweenthe piston and the second end member of the housing. An inlet port isdefined by the first end member of the housing and is in fluidcommunication with the first variable volume. A piston bypass channel isdisposed outside the cylindrical bore and is in fluid communication withthe inlet port. An outlet port is defined by the second end member ofthe housing, such that the outlet port is in fluid communication withthe piston bypass channel.

Another aspect of the present invention advantageously provides aninflatable inflatable cuff, a tube fluidly coupled to the inflatableinflatable cuff, and a pressure indicating device fluidly coupled to theinflatable inflatable cuff through the tube. The pressure indicatingdevice includes a housing defining a cylindrical bore therein, and apiston movably disposed within the cylindrical bore. The housingincludes a first portion that is permeable to visible light, a first endmember, and a second end member opposite the first end member. A firstvariable volume is defined by the cylindrical bore, the piston, and thefirst end member of the housing, and a second variable volume is definedby the cylindrical bore, the piston, and the second end member of thehousing, such that the second variable volume is sealed between thepiston and the second end member of the housing. An inlet port isdefined by the first end member of the housing and is in fluidcommunication with the first variable volume. A piston bypass channel isdisposed outside the cylindrical bore and is in fluid communication withthe inlet port. An outlet port is defined by the second end member ofthe housing, such that the outlet port is in fluid communication withthe piston bypass channel.

There has thus been outlined, rather broadly, certain embodiments of theinvention in order that the detailed description thereof herein may bebetter understood, and in order that the present contribution to the artmay be better appreciated. There are, of course, additional embodimentsof the invention that will be described below and which will form thesubject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of embodiments inaddition to those described and of being practiced and carried out invarious ways. Also, the phraseology and terminology employed herein, aswell as the Abstract, are for the purpose of description and should notbe regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. Therefore, the claimsshall be regarded as including such equivalent constructions insofar asthey do not depart from the spirit and scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents a schematic view of a pressure cuff system according toan embodiment of the present invention.

FIG. 2 presents a schematic view of a pressure cuff system according toanother embodiment of the present invention.

FIG. 3 presents a schematic view of an endotracheal tube systemaccording an embodiment of the present invention.

FIG. 4 shows a cross section of the endotracheal tube system illustratedin FIG. 3 along section 4-4.

FIG. 5 presents a perspective view of a pressure indicator according toan embodiment of the present invention.

FIG. 6 shows a left-side view of the pressure indicator in FIG. 5.

FIG. 7 shows a cross sectional view of the pressure indicatorillustrated in FIG. 6 along section 7-7.

FIG. 8 presents a perspective view of further aspects of a pressureindicator according to one or more embodiments of the present invention.

FIG. 9 shows a cross sectional view of another embodiment of thepressure indicator illustrated in FIG. 6 along section 7-7.

DETAILED DESCRIPTION

The invention will now be described with reference to the drawingfigures, in which like reference numerals refer to like partsthroughout. An embodiment in accordance with the present inventionprovides a pressure indicator for detecting an inflation pressureapplied to an inflatable cuff.

FIG. 1 presents a schematic view of a pressure cuff system 10 accordingto an embodiment of the present invention. The pressure cuff system 10includes an inflatable cuff 12 in fluid communication with a pressurizedfluid source 14 through a supply channel 16. The pressure cuff system 10further includes a pressure indicator 18 in fluid communication with thesupply channel 16, such that a flow of pressurizing fluid from thepressurized fluid source 14 flows through the pressure indicator 18 enroute to the inflatable cuff 12. The pressurizing fluid may include anyliquid fluid, such as water, or any gaseous fluid, such as air, forexample.

The pressure cuff system 10 may include a first valve 20 disposed in thesupply channel 16, and a second valve 24 branching off from the supplychannel 16 and in fluid communication therewith. In one embodiment ofthe present invention, the first valve 20 is a check valve oriented suchthat the first valve 20 permits flow only in a direction from thepressurized fluid source 14 toward the inflatable cuff 12. In anotherembodiment of the present invention, the first valve 20 is anormally-closed, spring-loaded isolation valve that is configured to beopened by a syringe luer engaging the pressure cuff system 10 as thepressurized fluid source 14. In yet another embodiment of the presentinvention, the valve 24 is a manually operated bleed valve. In still yetanother embodiment of the present invention, the valve 24 is aspring-loaded pressure relief valve that is configured to vent pressurefrom the inflatable cuff 12 at a threshold high pressure.

The pressurized fluid source 14 could include any pump, such as, forexample, a syringe, an elastic bulb, a rotary pump, or a positivedisplacement pump; a plenum pressurized with a fluid; combinationsthereof; or any other means for supplying a pressurized fluid known topersons with ordinary skill in the art. The inflatable cuff 12 couldinclude an elastic membrane or other structure that expands uponpressurization known to persons with ordinary skill in the art. Examplesof the inflatable cuff 12 include an endotracheal tube or a tracheostomytube.

FIG. 2 presents a schematic view of a pressure cuff system 10 accordingto an alternate embodiment of the present invention. In FIG. 2, thepressure indicator 18 is in fluid communication with the supply channel16 through a branch channel 25. Here, the pressure indicator 18 has aninlet in fluid communication with the supply channel 16 but no outlet.

Referring now to FIGS. 3 and 4, it will be appreciated that FIG. 3presents a schematic view of an endotracheal tube system 26 according anembodiment of the present invention; and FIG. 4 shows a cross section ofthe endotracheal tube system 26 illustrated in FIG. 3 along section 4-4.The endotracheal tube system 26 includes an elongated tube 28, defininga main lumen 30 (see FIG. 4) therethrough. The inflatable cuff 12 isdisposed around an outer periphery 32 of the elongated tube 28. In oneembodiment, the inflatable cuff 12 defines an annular volume therein,which surrounds the elongated tube 28.

The elongated tube 28 may further define an inflation lumen 34 (see FIG.4), which is fluidly coupled to a volume within the inflatable cuff 12.The supply channel 16 may be fluidly coupled to the inflation lumen 34,thereby effecting fluid communication between the inflatable cuff 12 andthe pressurized fluid source 14.

FIG. 5 presents a perspective view of a pressure indicator 18 accordingto an embodiment of the present invention. The pressure indicator 18includes a housing 36 and a piston 38 movably disposed within thehousing. The housing 36 defines an inlet port 40 and may define an exitport 42. The pressure indicator 18 may be fluidly coupled to the supplychannel 16 through both the inlet port 40 and the exit port 42 (see FIG.1), or coupled to the supply channel 16 through only the inlet port 40when there is no exit port 42 (see FIG. 2).

Referring now to FIGS. 6 and 7, it will be appreciated that FIG. 6 showsa left-side view of the pressure indicator 18 in FIG. 5; and that FIG. 7shows a cross sectional view of the pressure indicator illustrated inFIG. 6 along section 7-7. The housing 36 includes a barrel 44 disposedbetween an inlet end member 46 and an exit end member 48. An internalsurface of the barrel defines a bore 52 therein. In one embodiment ofthe present invention, the bore 52 has a generalized cylindrical shapeand extends along an axis 58 of the bore 52. In another embodiment ofthe present invention, the bore 52 has a circular cylindrical shape. Theexternal surface 60 of the barrel may or may not have the same shape asthe bore 52.

The piston 38 may engage the bore 52 of the barrel 44 through one ormore seals 54 disposed about a peripheral surface 56 of the piston. Inone embodiment of the present invention, the piston 38 includes only oneseal 54. In another embodiment of the present invention the piston 38includes at least two seals 54. However, it will be appreciated that thepiston 38 may incorporate any number of seals 54.

The one or more seals 54 may have an o-ring structure. The o-ringstructure could have a round cross section; a polygonal cross section,such as a square cross section; an elliptical cross section; a C-shapedcross section; a J-shaped cross section; a W-shaped cross section, orother o-ring cross section known to persons with ordinary skill in theart. Further, the one or more seals 54 may be disposed within one ormore circumferential grooves 62 defined by the peripheral surface 56 ofthe piston 38.

An interface 64 between the barrel 44 and the inlet end member 46 formsa fluid-tight seal therebetween. Further, an interface 66 between thebarrel 44 and the exit end member 48 may form a fluid-tight sealtherebetween. The barrel 44 may be joined to the inlet end member 46 orthe exit end member 48 by welding, adhesive bonding, threadedconnection, or other joining methods known to persons with ordinaryskill in the art.

The bore 52, the inlet end member 46, and the piston 38 define a firstvariable volume 72. Further, the bore 52, the exit end member 48, andthe piston 38 define a second variable volume 74. In one embodiment ofthe present invention, the second volume 74 is completely sealed betweenthe bore 52, the exit end member 48, and the piston 38. Optionally, inthe alternative, the exit end member 48 defines a bleed channel 76,which is in fluid communication with the second volume 74 and an ambientenvironment of the pressure indicator 18; and a resilient member 78 (seeFIG. 9) biases the piston 38 toward the inlet end member 46. Theresilient member 78 could be a compression spring disposed within thesecond volume 74 (as shown in FIG. 9), or a tension spring disposedwithin the first volume 72 (not shown), for example.

An internal portion 80 of the inlet end member 46 defines a first fluidchannel 82 therethrough. The first fluid channel 82 is in fluidcommunication with the inlet port 40 and the first volume 72. Theinternal portion 80 of the inlet end member 46 may further define arelief port 84 containing a pressure relief device 86. The pressurerelief device could include a frangible element such as a burst disk, aresilient stopper press fit into the relief port 84, a pressure actuatedvalve, or other pressure relief device known to persons of ordinaryskill in the art. When the pressure relief device 86 is activated by anexcess of pressure within the first fluid channel 82, the first fluidchannel is in fluid communication with the ambient environment of thepressure indicator 18 via the relief port 84.

The housing 36 further includes a piston bypass tube 88 defining abypass channel 90 therein. In one embodiment of the present invention,the piston bypass tube 88 is a straight tube having an axis 92 that issubstantially parallel to the axis 58 of the bore 52. In anotherembodiment of the present invention, a distance 94 between the axis 92of the piston bypass tube 88 and the axis 58 of the bore 52 is greaterthan the sum of an outer diameter 96 of the barrel 44 and an outerdiameter 98 of the piston bypass tube 88 divided by two (distance94>[diameter 96+diameter 98]/2).

An outer surface 102 of the barrel 44 and an outer surface 104 of thepiston bypass tube 88 may form a gap 100 therebetween. In oneembodiment, the gap 100 is not greater than the outer diameter 98 of thepiston bypass tube 88. Alternatively, there may be no gap between theouter surface 104 of the piston bypass tube 88 and the outer surface 102of the barrel 44.

An internal surface 106 of the exit end member 48 may further define asecond fluid channel 108 therein. The second fluid channel 108 is influid communication with the bypass channel 90 and the exit port 42,such that the exit port 42 may be in fluid communication with aninflatable cuff 12 through the supply channel 16 (see FIGS. 1 and 3). Inone embodiment of the present invention, the second fluid channel 108 isnot in fluid communication with the second volume 74.

An axis 110 of the first fluid channel 82 may be substantially coaxialwith an axis 112 of the second fluid channel 108. Further the axis 110of the first fluid channel 82, the axis 112 of the second fluid channel108, and the axis 58 of the bore 52 may all be substantially coaxialwith one another.

It will be appreciated that the parallel alignment and close proximityof the piston bypass tube 88 relative to the barrel 44 results in anadvantageously compact, in-line, configuration for the pressureindicator 18. It will also be appreciated that substantially coaxialalignment of the axis 58 of the bore 52 with either of the axis 110 ofthe first fluid channel 82, or the axis 112 of the second fluid channel108 may further promote an advantageously compact arrangement thatbeneficially accommodates in-line installation as part of a fluidchannel.

FIG. 8 presents a perspective view of further aspects of a pressureindicator according to one or more embodiments of the present invention.As illustrated in FIG. 8, at least a portion 114 of the barrel 44 ispermeable to visible light, such that the piston 38 is visible throughthe portion 114. The portion 114 may be transparent or merelytranslucent. The barrel 44 may be made from materials that are permeableto visible light such as, for example, glass, clear polymers,combinations thereof, or other structural materials permeable to visiblelight that are known to persons of ordinary skill in the art.

Pressure indicia 116 may be disposed on the barrel 44. In oneembodiment, the pressure indicia 116 are disposed adjacent to theportion 114 of the barrel 44 that is permeable to visible light. Inanother embodiment, the pressure indicia 116 are themselves permeable tovisible light, such that the piston 38 is visible through both thebarrel 44 and the pressure indicia 116. The pressure indicia 116 mayinclude a plurality of discrete zones 118 disposed along a axialdirection of the barrel 44. In one embodiment of the present invention,the plurality of discrete zones 118 includes a first zone 120, a secondzone 122, and a third zone 124, all arranged sequentially along theaxial direction of the barrel 44. In another embodiment of the presentinvention, the first zone 120 has a yellow color, the second zone 122has a green color, and the third zone 124 has a red color.

When a pressure inside the first volume 72 is atmospheric pressure, thepiston location within the bore 52 may be biased toward the inlet endmember 46. The piston may be biased toward the inlet end member by abalance of pressure between the first volume 72 and the second volume74; the resilient member 78 acting on the piston 38; a charge of gasstored within the second volume 74 having a pressure greater thanatmospheric pressure; or combinations thereof, for example.

As pressure is applied from the pressurized fluid source 14 to the inletport 40 of the pressure indicator 18 through the supply channel 16, thepressure imparts a force tending to displace the piston 38 in adirection along the axis 58 of the bore 52 from the inlet end member 46toward the exit end member 48. Displacement of the piston in a directiontoward the exit end member 48 performs work on gas disposed within thesecond volume 74, the resilient member 78, or combinations thereof,thereby imparting a reaction force against the pressure force impartedonto the piston by the pressure in the first volume. Thus, an axiallocation 126 of the piston 38 within the bore 52 is functionally relatedto the pressure within the first volume.

It will be appreciated that the functional relationship between theaxial location 126 of the piston within the bore 52 and a pressurewithin the first volume 72 does not depend on structural parameters ormaterial properties of a complex bellows element. Accordingly, apparatusand methods for indicating pressure according to embodiments of thepresent invention promote measurement accuracy over conventionalapproaches by eliminating sources of manufacturing variation that canaffect calibration.

In one embodiment, the piston 38 has a hollow structure and is made froma light weight material such as a polymer, for example. In turn, thepiston 38 can be made having a very low weight, such that accuracy ofthe pressure indicator 18 is not sensitive to a spatial orientation ofthe pressure indicator 18 with respect to gravity.

The piston 38 may include an indicator mark 128, which defines areference position on the piston 38 for identifying the axial location126 of the piston 38 within the pressure indicator 18. Accordingly, alocation of the indicator mark 128 relative to the pressure indicia 116may provide an indication of pressure within the first volume 72 of thepressure indicator 18.

In one embodiment of the present invention, the first zone 120 of thepressure indicia 116 corresponds to a range of pressures that are belowa first target pressure, the third zone 124 corresponds to a range ofpressures that are above a second target pressure, and the second zone122 corresponds to a range of acceptable pressures between the firsttarget pressure and the second target pressure. Accordingly, theindicator mark 128 disposed within the first zone 120 may indicate thata measured pressure is low, the indicator mark 128 disposed within thesecond zone 122 may indicate that a measured pressure is acceptable, andthe indicator mark disposed with the third zone 124 may indicate thatthe measured pressure is high.

Although the pressure indicator 18 is useful to indicate a fluidpressure within a pressure cuff system 10, the pressure indicator 18 canalso be used to measure fluid pressure in other systems that couldbenefit from either quantitative or qualitative indication of a fluidpressure.

The many features and advantages of the invention are apparent from thedetailed specification, and thus, it is intended by the appended claimsto cover all such features and advantages of the invention which fallwithin the true spirit and scope of the invention. Further, sincenumerous modifications and variations will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and operation illustrated and described, andaccordingly, all suitable modifications and equivalents may be resortedto, falling within the scope of the invention.

What is claimed is:
 1. A pressure indicating device, comprising: ahousing defining a cylindrical bore therein, the housing including afirst portion that is permeable to visible light, a first end member,and a second end member opposite the first end member; a piston movablydisposed within the cylindrical bore, a first variable volume defined bythe cylindrical bore, the piston, and the first end member of thehousing; a second variable volume defined by the cylindrical bore, thepiston, and the second end member of the housing, such that the secondvariable volume is sealed between the piston and the second end memberof the housing; an inlet port defined by the first end member of thehousing and in fluid communication with the first variable volume; apiston bypass channel disposed outside the cylindrical bore and in fluidcommunication with the inlet port; and an outlet port defined by thesecond end member of the housing, the outlet port in fluid communicationwith the piston bypass channel.
 2. The pressure indicating device ofclaim 1, wherein a longitudinal axis of the piston bypass channel issubstantially parallel to a longitudinal axis of the cylindrical bore.3. The pressure indicating device of claim 1, wherein an axis of theinlet port is substantially coaxial with the longitudinal axis of thecylindrical bore.
 4. The pressure indicating device of claim 1, whereinan axis of the outlet port is substantially coaxial with thelongitudinal axis of the cylindrical bore.
 5. The pressure indicatingdevice of claim 1, further comprising at least one seal disposed betweenthe piston and the cylindrical bore.
 6. The pressure indicating deviceof claim 5, wherein the at least one seal consists of a plurality ofseals.
 7. The pressure indicating device of claim 1, further comprisingpressure indicia disposed on the housing.
 8. The pressure indicatingdevice of claim 7, further comprising an indicator mark on the piston,such that a location of the indicator mark with respect to the pressureindicia indicates a pressure in the first variable volume.
 9. Thepressure indicating device of claim 7, wherein the pressure indiciademarcates three pressure magnitude regions, the three pressuremagnitude regions disposed consecutively along a direction of thelongitudinal axis of the cylindrical bore of the housing.
 10. Thepressure indicating device of claim 7, wherein the pressure indicia aredisposed on the first portion of the housing that is permeable tovisible light, and the pressure indicia are permeable to visible light,such that the piston is visible through the pressure indicia and thefirst portion of the housing.
 11. The pressure indicating device ofclaim 1, further comprising a resilient member disposed on the piston,such that the resilient member biases the piston toward the first endmember.
 12. The pressure indicating device of claim 11, wherein theresilient member is a compression spring disposed in the second variablevolume.
 13. The pressure indicating device of claim 11, wherein theresilient member is a tension spring disposed in the first variablevolume.
 14. An inflatable cuff apparatus, comprising: an inflatablecuff; a tube fluidly coupled to the inflatable cuff; and a pressureindicating device fluidly coupled to the inflatable cuff through thetube, the pressure indicating device including a housing defining acylindrical bore therein, the housing including a first portion that ispermeable to visible light, a first end member, and a second end memberopposite the first end member; a piston movably disposed within thecylindrical bore, a first variable volume defined by the cylindricalbore, the piston, and the first end member of the housing; a secondvariable volume defined by the cylindrical bore, the piston, and thesecond end member of the housing, such that the second variable volumeis sealed between the piston and the second end member of the housing;an inlet port defined by the first end member of the housing and influid communication with the first variable volume; a piston bypasschannel disposed outside the cylindrical bore and in fluid communicationwith the inlet port; and an outlet port defined by the second end memberof the housing, the outlet port in fluid communication with the pistonbypass channel.
 15. The inflatable cuff apparatus of claim 14, wherein alongitudinal axis of the piston bypass channel is substantially parallelto a longitudinal axis of the cylindrical bore.